The present invention generally relates to the simultaneous formation of multiple openings through a substrate, and more particularly to a method and apparatus for simultaneously directing multiple streams of abrasive particles onto a substrate in order to form a plurality of openings therethrough.
The continuing development of sophisticated, miniaturized electronic systems has created a corresponding need for rapid and accurate manufacturing methods. Many electronic devices include components which must be produced with multiple openings/ports therethrough. For example, thermal ink jet cartridges typically include a substrate manufactured of silicon, glass, or the like to which an orifice plate and a plurality of jetting resistors are attached. The substrate normally includes one or more feed openings which enable ink to pass from a storage reservoir behind the substrate to the orifice plate and resistors. These openings are very small, and must be made to precise specifications.
Many methods have been used to produce the openings described above. For example, feed openings in the substrates of thermal ink jet cartridges have been made using conventional laser and/or ultrasonic drill systems However, these methods have not proven to be efficient or economical. Another method involves the formation of one opening at a time using a process known as "abrasive jet machining." This process involves the use of a nozzle which directs a stream of gas-accelerated abrasive particles (10-50 microns in diameter) at a selected substrate. The method can make openings as narrow as 0.005 inch or abrade an area of several square inches as discussed in an article by Ingulli, C. N. entitled "Abrasive Jet Machining," published in The Tool and Manufacturing Engineer, pp. 28-33 (Nov. 1987).
Using this process, each opening is made one at a time by a single nozzle. To cause the abrasive particles to be ejected from the nozzle, an apparatus is used which is attached to a source of pressurized gas (e.g. compressed air). The apparatus also includes a mixing chamber containing a supply of abrasive particles (e.g. aluminum oxide, silicon carbide, dolomite, and/or sodium bicarbonate). Activation of the apparatus causes a vibrator in the mixing chamber to operate. At essentially the same time, a valve within the system is opened, causing gas to flow through the apparatus and out of the nozzle. Vibration of the chamber causes some of the abrasive particles to escape from the mixing chamber through small openings therein so that the particles come in contact with the gas stream moving through the apparatus. As a result, the gas stream carries the particles through the nozzle at a high velocity (e.g. a flow rate of about 2-20 grams/minute). The particles then contact the substrate, causing the formation of an opening therethrough.
Most systems used to perform abrasive jet machining include controls for regulating gas pressure and the flow of particulate materials. Both of these factors independently influence the cutting action of the system. Conventional systems use an individual nozzle, each nozzle including a single orifice therein. The nozzle may be straight or bent to form a 90 degree angle. Exemplary materials used to produce the nozzles include tungsten carbide and sapphire. According to Ingulli, supra, tungsten carbide nozzles typically last between about 13-30 hours, while sapphire nozzles last for about 300 hours.
Other factors which influence cutting efficiency are the distance from the nozzle tip to the substrate, and the angle between the substrate and nozzle.
In general, abrasive jet machining offers numerous benefits in the production of electronic components. It is capable of forming an opening in a substrate with a high degree of accuracy, while avoiding damage to surrounding components and materials. Also, it is capable of cutting openings in many different types of substrates without the generation of excessive heat. Furthermore, it allows for improved relative placement accuracies during the production process. Additional general information regarding abrasive jet machining is disclosed in U.S. Pat. Nos. 2,907,200; 3,257,759; 3,514,851; 4,188,247; 4,232,059; and 4,272,612. Information is also provided in U.K. Patent 1,187,976; U.K. Patent Application 2,164,879A, and Japanese Patent Specification 59-030669.
The present invention involves an improved nozzle apparatus for abrasive jet machining. Specifically, the improved nozzle apparatus enables the simultaneous cutting of multiple openings in a substrate which represents an advance in the art, compared with conventional, single-bore systems. Other benefits of the invention include improved nozzle orifice size and configuration.